Wireless signaling apparatus



April 4, 1939. J. ROBINSON 5 WIRELESS SIGNALING APPARATUS Filed Nov. 16, 1936 ;0 1 1 2,5 1 I I SIGNAL ACCEPTOR DE TECT05|!, LEAMPLI H54: DETECTOR FILTER F SEEECTIVE CIRCUIT osmmoa PHASE -16 CONTROL L VOLUME CON TROL 17 I a I 3 SIGNAL GELECT'IVE ACCEPTOR DETECTOR n LEAMPLlFIER ETECTR3 1 ll I FILTER.

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VOLUME OSCILLATOR CONTROL T 10 g1 25 g4 SIGNAL SELEC'TIVE I ACCEPTOR DETECTOR R LF'AMPUHEh DETECTOR ll 18 ll FILTER FILTER PHASE --1 CONTROL 5 5 1% VOLUME OSCI LLATO CONTR 0L DETECTOR 3% mveufor Dumas Rows 1Q wmmfixqmh q Patented Apr. 4, 1939 UNITED STATES OFFICE Application November 16, 1936, Serial No. 111,166 In Great Britain November 22, 1935 9 Claims.

This invention relates to wireless signaling apparatus and is concerned with such apparatus in which there is a frequency-changing apparatus for the applied signals. The invention is particularly applicable to the wireless apparatus of the superheterodyne type and in receivers of this type it is convenient for practical reasons to provide the necessary selectivity for modern conditions in the intermediate frequency stage. It is preferable under certain circumstances to have selectivity in an earlier stage of the receiver and one object of the invention is to achieve this result.

According to the present invention there is provided in a wireless apparatus such as a receiver having a frequency-changer comprising a valve detector and oscillator, means for applying a portion of the signal output derived from the frequency-changer either directly or indirectly to the oscillator in order to change the signal amplitude as applied to the detector. In this manner a form of retroaction is obtained which may provide an effective increase in selectivity.

According to a further feature of the invention means is provided for reducing the percentage modulation of the signals fed back to the oscillator. In this manner the signals fed back to the oscillator consist mainly or wholly of the converted carrier-frequency which, when combined with the frequency of the local oscillator, serves to produce a frequency component of the same frequency as the carrier-wave of the initially applied signals, which component is effective for instance by means of the normal coupling between the oscillator and the detector, to

augment the incoming carrier frequency at the input of the detector to increase the selectivity at this part of the receiver. The means aforesaid for reducing the percentage modulation of the signals fed back to the oscillator, may conveniently comprise a highly-selective device such as a piezo-electric crystal. 7

In a modification, an additional detector is provided coupled to the oscillator, in combination with means coupling the output from this detector to the input of the frequency-changer or to a preceding stage of the apparatus.

A feature of the invention consists in the provision of means for adjusting or controlling the phase of the retroactive signals applied to the oscillator, in order to ensure the required phase relationship of the signals applied to the frequency-changer, and the signals fed back by retroaction. I

It is convenient to provide means interposed between the oscillator and the detector, or each of them, to suppress signals'of unwanted frequencies. Means is also preferably provided to control automatically the volume of the signals fed back to the oscillator from the output of the frequency-changer.

Several embodiments of the invention are i1- lustrated diagrammatically and by way of example in the accompanying drawing, in which:

Figure 1 shows a wireless receiver in which the feed-back is derived directly from the output of the frequency-changer;

Figure 2 shows a modification in which the feed-back is derived from the output of a selective intermediate frequency amplifier of the receiver, and

Figure 3 shows a further modification employing a separate detector for producing, in combination with the oscillator, the required retroactive frequency.

Like references indicate like parts in the several figures of the drawing.

Referring to Figure 1, there is shown diagrammatically a wireless receiver of the super-heterodyne type comprising a signal-acceptor and preselective amplifier In, a frequency-changer consisting of a detector II and associated local oscillator l2, an intermediate frequency amplifier l3 and a second detector I 4. A portion of the output of the first detector H at the intermediate frequency is applied to a selective circuit I5 comprising for instance a mechanically resonant device such as a piezo-elec'tric crystal. The characteristics of this selective circuit l5 are so chosen as to select substantially only the intermediate carrier-frequency of the signals. The output of the selective device I5 is applied through phase-controlling means 16 and volumecontrolling means I! to the oscillator l2.

The phase-controlling means It may be of any convenient known form for providing an adjustment of the signals to vary the phase of the intermediate-frequency carrier-wave signals with regard to the incoming signals. For instance, in the case where a piezo-electric device is employed, and a variable condenser is connected with the 1 piezo-electric device in a bridge system for balancing the effects of the capacity of the piezoelectric device, as described in United States Patent No. 1,898,895, the required phase adjustment may be effected by adjusting the capacity of the condenser. The volume-controlling means I! is also of any convenient known form and may consist of a limiting device or alternatively an amplifying means controlled as regards its amplification, automatically in the known manner according to the intensity of the signal output of the detector I I in order to minimise undesired intensity variations.

The signals thus applied to the oscillator I2 and consisting mainly or wholly of the intermediate carrier-frequency, serve to modulate the output of the local oscillator I2. In consequence, there is produced a frequency component of the same frequency as the carrier-frequency or the initially applied signals, and this frequency component is effective through the normal coupling between the oscillator and the detector in a receiver of the super-heterodyne type to augment the incoming carrier-frequency at the input of the detector II. The retroactive carrier component applied to the detector II is arranged to be in phase with the carrier component of the incoming signals by adjustment of the phasecontrol I6.

The increased intensity of the carrier component at the detector II thus serves to provide an increase in selectivity at this part of the receiver, on the basis of the known homodyne method. A filter I8 is preferably provided between the detector II and the oscillator I2 to suppress unwanted frequencies, including the intermiate carrier-frequency.

In the arrangement indicated in Figure 1 the intermediate-frequency amplifier is not necessarily of high-selectivity. The arrangement shown in Figure 2 is similar to that shown in Figure 1, except that in this case the super-heterodyne receiver comprises an intermediate-frequency amplifier 23 which is in itself highlyselective and comprises for instance a mechanically resonant device such as a piezo-electric crystal, In this case the retroactive energy is derived from the output of this selective intermediate-frequency amplifier 23 and is applied through the phase-control means It to the local oscillator I2 in the manner described with reference to Figure 1.

Instead of using the normal detector H associated with the oscillator I2 for producing the re-conversion of the signals to the original frequency for retroaction, a separate detector may be used in association with the oscillator. In Figure 3 there is shown an arrangement which differs from Figure 2 in the provision of an additional rectifier 24 to which is applied a portion of the output of the oscillator I2 as modulated by the intermediate-frequency signals from the selective amplifier 23. There is thus obtained at the output of the detector 24 a frequency component of the same frequency as the carrierfrequency of the applied signals and this component is applied, through a filter 25 for suppressing other frequencies, to any convenient part of the signal-acceptor and preselective amplifier I0, or alternatively, to the input of the detector I I as in the preceding examples. Thus, with this arrangement also, the carrier-frequency of the incoming signals is intensified to obtain the bene fits of increased effective selectivity according to the homodyne method. The filter I8 is in this case conveniently constructed to pass only the said and also tuned circuits for the additional oscillator, when employed, are conveniently ganged for simultaneous adjustment with the normal tuning circuits of the receiver.

It will be understood that amplifying means may be included as required for the retroactive signals, for instance for the signals fed back to the oscillator I2. Furthermore, the oscillator and the detector of a frequency-changer have been described as separate entities, but it will be understood that the two devices may be combined in known manner for instance in an apparatus comprising a single multi-electrode thermionic Valve operating as a detector and also servin to produce the required local oscillations.

I claim:-

1. High frequency signaling apparatus comprising a frequency-changer having a thermionic valve detector and oscillator, to which detector wave-signals are applied, means for applying the beat frequency signals derived from the frequency-changer to the said oscillator in order to change the amplitude of the signal input to the said detector.

2. High frequency signaling apparatus comprising a frequency-changer having a thermionic valve detector and oscillator, to which detector modulated carrier-wave signals are applied, and retroactive means for applying a portion of the signal output derived from the frequencychanger to the said oscillator, said retroactive means comprising means for reducing the percentage modulation of the retroactive signals.

3. High frequency signaling apparatus comprising a frequency-changer having a thermionic valve detector and oscillator to which detector, Wave signals are applied, mechanically resonant signal-selective means for the signal output of the frequency-changer, and means for applying a portion of the signal output derived from the frequency-changer through said selective means to the said oscillator.

4. High frequency signaling apparatus comprising a frequency-changer having a thermionic valve detector and oscillator, to which detector wave signals are applied, retroactive means for applying a portion of the signal output derived from the frequency-changer to the said oscillator in order to change the amplitude of the signal input to the said detector, and means for adjusting the phase of the signals applied to the oscillator by said retroactive means.

5. High frequency signaling apparatus comprising a frequency-changer having a thermionic valve detector and oscillator, to which detector wave signals are applied, means for applying a portion of the signal output derived from the frequency-changer to the said oscillator in order to change the amplitude of the signal input to the said detector, and means electrically interposed between said oscillator and said detector to suppress the output'frequency of the said frequencychanger.

6. High frequency signaling apparatus comprising a frequency-changer having a thermionic valve detector and oscillator, to which detector wave signals are applied, retroactive means for applying a portion of the signal output derived from the frequency-changer to the said oscillator in order to change the amplitude of the signal input to the said detector, and means to control automatically the volume of signals fed beck to the oscillator from thexoutput of the frequency-changer by said retroactive means.

'7. High frequency signaling apparatus comprising a signal-acceptor, a frequency-changer to which the output of said signal-acceptor is applied, said frequency-changer comprising a thermionic valve detector and oscillator, means for applying a portion of the signal output derived from the frequency-changer to modulate the local oscillations produced by the said oscillator, an additional detector, means applying a portion of the modulated oscillator output to said additional detector, and means applying the output of said additional detector to said signal-acceptor.

8. High frequency signaling apparatus comprising a signal-acceptor, a frequency-changer to which the output of said signal-acceptor is applied, said frequency-changer comprising a thermionic valve detector and oscillator, means for applying a portion of the signal output derived from the frequency-changer to modulate the local oscillations produced by the said oscillator, an additional detector, means app ng, a

portion of the modulated oscillator output to said additional detector, means applying the output of said additional detector to said signal-acceptor, means electrically interposed between the oscillator and the detector to suppress the output frequency of the frequency-changer, and means interposed between the said detector and the signal-acceptor to pass only the initial carrier frequency.

9. A high frequency signaling receiver of the heterodyne type comprising a frequency-changer having a thermionic valve detector and oscillator, highly selective means comprising a piezo-electric device for the intermediate frequency signal output of the frequency-changer, a second detector for the intermediate frequency signals and retroactive means for feeding a portion of the signal output of said signal selective means to the said oscillator.

JAMES ROBINSON. 

